The Antibody Response to SARS-CoV-2 Infection

Area of Science:

• Immunology
• Infectious Diseases
• Virology

Background:

• Antibody testing for SARS-CoV-2 is crucial for COVID-19 diagnosis and population serosurveys.
• Assessing antibody magnitude and persistence is key to understanding immunity duration.

Purpose of the Study:

• To develop and evaluate a SARS-CoV-2-specific immunofluorescent antibody (IFA) assay.
• To compare IFA performance against nucleic acid testing (NAT) for COVID-19 diagnosis.

Main Methods:

• Developed and prospectively evaluated a SARS-CoV-2-specific IFA assay for IgG, IgA, and IgM.
• Compared IFA results with NAT on respiratory samples from suspected COVID-19 cases.
• Measured neutralizing antibody responses in a subset of samples.

Main Results:

• The IFA assay demonstrated high sensitivity (91.3%) and specificity (98.9%) for detecting SARS-CoV-2 antibodies ≥14 days post-symptom onset.
• The median antibody detection window was 10.2 days after illness onset.
• Combining IgG and IgA detection significantly improved the positive predictive value to 96.8%.

Conclusions:

• SARS-CoV-2-specific antibody measurement by IFA is an accurate diagnostic method.
• Serological testing should be integrated into COVID-19 diagnostic strategies.
• While robust antibody responses are common, their duration and impact on immunity require further investigation.